This multi-disciplinary project will provide, for the first time, a detailed view of the structural and functional relationships between several key proteins and enzymes in lipid processing and metabolic pathways. Specifically, we will focus our efforts on investigating the muscle and intestinal fatty acid binding proteins (I-FABP) and the yeast and intestinal acyl CoA synthetases, four proteins involved in the intracellular fatty acid transfer pathway, as well as the ileal lipid binding protein and farnesyl pyrophosphate synthetase, proteins involved in sterol biosynthesis. Further studies will explore the structural and functional properties of a form of human I-FABP which is linked to insulin resistance and non- insulin dependent diabetes mellitus, NIDDM, in individuals that express this protein. Our studies will employ high resolution x-ray and neutron crystallography to determine the precise structures of the protein:water:lipid complexes we are studying. Differential scanning and titration calorimetry will be employed in order to analyze the energetics of lipid binding and protein stability. Site-directed mutagenesis will be utilized to dissect the role of specific amino acid sidechains in the chemical, thermodynamic and structural properties of proteins under investigation. Finally, kinetic analyses will permit us to determine the role of FABPs in the delivery of fatty acids to enzymes involved in fatty acid processing pathways.